Current-induced atomic dynamics, instabilities, and Raman signals: Quasiclassical Langevin equation approach

TY - JOUR

T1 - Current-induced atomic dynamics, instabilities, and Raman signals

T2 - Quasiclassical Langevin equation approach

AU - Lu, Jing Tao

AU - Brandbyge, Mads

AU - Hedegård, Per

AU - Todorov, T.N.

AU - Dundas, D.

PY - 2012/6/25

Y1 - 2012/6/25

N2 - We derive and employ a semiclassical Langevin equation obtained from path integrals to describe the ionic dynamics of a molecular junction in the presence of electrical current. The electronic environment serves as an effective nonequilibrium bath. The bath results in random forces describing Joule heating, current-induced forces including the nonconservative wind force, dissipative frictional forces, and an effective Lorentz-type force due to the Berry phase of the nonequilibrium electrons. Using a generic two-level molecular model, we highlight the importance of both current-induced forces and Joule heating for the stability of the system. We compare the impact of the different forces, and the wide-band approximation for the electronic structure on our result. We examine the current-induced instabilities (excitation of runaway "waterwheel" modes) and investigate the signature of these in the Raman signals.

AB - We derive and employ a semiclassical Langevin equation obtained from path integrals to describe the ionic dynamics of a molecular junction in the presence of electrical current. The electronic environment serves as an effective nonequilibrium bath. The bath results in random forces describing Joule heating, current-induced forces including the nonconservative wind force, dissipative frictional forces, and an effective Lorentz-type force due to the Berry phase of the nonequilibrium electrons. Using a generic two-level molecular model, we highlight the importance of both current-induced forces and Joule heating for the stability of the system. We compare the impact of the different forces, and the wide-band approximation for the electronic structure on our result. We examine the current-induced instabilities (excitation of runaway "waterwheel" modes) and investigate the signature of these in the Raman signals.

U2 - 10.1103/PhysRevB.85.245444

DO - 10.1103/PhysRevB.85.245444

M3 - Journal article

SN - 2469-9950

VL - 85

SP - 245444

JO - Physical Review B

JF - Physical Review B

IS - 4

ER -